This invention relates generally to a blow molding apparatus for blow molding hollow articles such as plastic bottles.
Blow molding machines for blow molding hollow articles such as plastic bottles are known to include parison extruders configured to continuously extrude tubular parisons vertically downward through a parison extruder head. It is also known for a blow molding apparatus of this type to include two blow molds supported on trolleys. A drive system alternately moves the trolleys to transport each blow mold into a position aligned with the parison extruder head in a parison receiving position to receive parison from the parison extruder.
Each blow mold includes a blow mold cavity shaped to complement a desired exterior shape of a hollow article to be formed in the mold. Each blow mold and blow mold cavity is split into two parts that are movable away from one another to an open position that allow the mold to receive a length of parison from the parison extruder. The mold parts are movable back toward each other to a closed or clamped position around such a length of parison.
It is also known for mold parts to be moved apart by the drive system in advance of moving the mold into the parison receiving position. This allows an article take-out mechanism to extract a blown article from each mold after hardening and allows an in-mold labeler to place a label on an inner wall of the mold cavity.
A blow pin may be supported on each trolley adjacent an associated blow mold carried on each trolley. Each blow pin is movable into a position aligned with an upper opening in its associated mold cavity. Each blow pin is also supported for insertion into its associated mold cavity through the upper opening of that mold cavity. Each blow pin is configured to inject gas into a length of parison supported within its associated mold cavity to expand the parison against inner walls of the mold cavity to form a hollow article to a desired shape as is well known in the art.
Some blow molding machines of this type also include two ramped surfaces disposed adjacent and beneath the parison extruder head. The trolleys are each movably supported on one of the ramped surfaces such that the trolleys are elevated at upper end of their respective ramped surface when their respective molds are disposed in the parison receiving position. The ramps cause the blow molds to descend as they move laterally away from the extrusion head after severing or xe2x80x9ccapturingxe2x80x9d a length of parison for blow molding. The downward component of this motion prevents the continuously advancing parison still flowing from the extrusion head from being pulled sideways and distorted due to contact with and sticking to an upper surface of the mold as the trolley moves the mold away from the parison receiving position.
What is needed is a blow molding apparatus for blow molding hollow articles such as plastic bottles that can dedicate a higher percentage of total cycle time to cooling the parison without reducing the number of blown articles produced by the apparatus over a given period of time.
A blow molding apparatus for blow molding hollow articles such as plastic bottles is provided that includes a -parison extruder configured to extrude a tubular parison along an extrusion axis. First and second blow molds are supported for movement into a parison receiving position aligned with the extrusion axis and for movement out of the parison receiving position in respective first and second radial directions. Each blow mold is configured to receive a length of parison extending from the parison extruder when in the parison receiving position, to enclose and sever the length of parison, to contain and shape the parison during blow molding and to release the blown article in an article take-out position. The apparatus includes a drive configured to alternately move the first and second blow molds into the parison receiving position, from the parison receiving position in the respective first and second radial directions and back to the parison receiving position.
Unlike the prior art, at least one of the first and second blow molds is supported for movement into the parison receiving position from a third radial direction angularly spaced between the first and second radial directions.
Cycling the molds back into the parison receiving position from directions different from those used to move the molds out of the parison receiving position allows the two blow molds to be cycled through a common workstation such as an article take-out station and/or an in-mold labeling station.
The invention also includes a method for blow molding hollow articles such as plastic bottles. According to this method one can blow mold hollow articles such as plastic bottles by first providing a blow molding apparatus including a parison extruder and first and second blow molds, each blow mold being configured to contain and shape lengths of parison during blow molding and to release resulting blown articles in an article take-out position and a drive configured to alternately move the first and second blow molds between the parison receiving position and an article take-out position. The first blow mold is caused to receive a first length of parison from the extruder while the first blow mold is in the parison receiving position. The drive is then actuated to move the first blow mold out of the parison receiving position in a first radial direction and to move the first blow mold to the article take-out position. The first blow mold is then caused to release a blown article formed from the first length of parison. The drive is actuated to move the second blow mold to the parison receiving position in a third radial direction angularly spaced from the first radial direction after the first blow mold has moved out of the parison receiving position. The second blow mold is then caused to receive a second length of parison from the extruder. The drive then actuated to move the second blow mold out of the parison receiving position in a second radial direction angularly spaced from the first and third radial directions and to move the second blow mold to the article take-out position. The second blow mold is then caused to release a blown article formed from the second length of parison. The drive is actuated to move the first blow mold back into the parison receiving position from the third radial direction after the second blow mold has moved out of the parison receiving position.